(1) Field of the Invention
The present invention relates to an automatic painting apparatus for spray painting articles such as automobile bodies and casings for household electrical appliances. More particularly, the invention relates to an automatic painting apparatus comprising a spraying region having ceiling supply openings for delivering a ventilating gas in downward laminar flows, a portal framework disposed in the spraying region and including a pair of vertical frames disposed on both sides of a conveying track of articles under a spraying treatment, and a cross frame extending between the vertical frames over and across the article conveying track, spray guns attached to the cross frame for spraying paint downwardly, and a spray gun moving mechanism mounted on the portal framework for reciprocating the spray guns longitudinally of the cross frame.
(2) Description of the Prior Art
In known automatic painting apparatus as noted above, the spray guns attached to the cross frame for spraying paint downwardly are reciprocated longitudinally of the cross frame (i.e. transversely of the article conveying track). More particularly, as shown in FIGS. 7 and 8, spray guns 6 are attached to a longitudinally immovable cross frame 5 to be displaceable longitudinally of the cross frame 5 by means of an oscillation guide mechanism 36, an oscillation link mechanism, a roller mechanism or other movable support mechanism. Spray guns 6 are reciprocated by a drive motor 23 through a crank mechanism 37 or other transmission mechanism supported by the cross frame 5.
In the drawings, number 8 indicates ceiling supply openings for delivering a ventilating gas in downward laminar flows. Number 4 indicates vertical frames disposed on both sides of an article conveying track F. Reference A indicates an article under a spraying treatment.
The ventilating gas is delivered through the ceiling supply openings in downward laminar flows in order to stabilize paint spraying with respect to the article. With the above construction, however, the ventilating gas flows are obstructed by the movable support mechanism for displaceably attaching the spray guns to the cross frame and by the crank mechanism or other transmission mechanism supported by the cross frame, whereby disturbances take place with the laminar flows of the ventilating gas downwardly of these mechanisms. In particular, a greater resistance occurs with the ventilating gas flows on the lefthand side than the righthand side of FIG. 8. As a result, the paint spraying state becomes disordered, giving rise to the problem of uneven spraying and low paint adhesion efficiency.